Phosphorus Dynamics: Relative Contributions by Bacteria and Zooplankton to Recycling Processes in Lakes Michigan, Huron and Erie

9508087众所周知，北美五大湖生态系统中磷的可获得性和供应率的雷曼差异是控制生产力、生物量发展和物种组成的主要因素。尽管如此，夏季所有五大湖的表层磷浓度都很低，放射性示踪剂研究表明，由于生物过程，周围水池的周转时间为几分钟至几十分钟。夏季生产性月份的现场浓度通常被证明难以准确测量，但似乎与海洋对氨动态的观察一样，细菌主导着环境水平的通量，而当浓度适度增加时，浮游植物占主导地位。在不同营养条件的五大湖中，示踪剂P的周转动态和平衡分配存在差异，个别五大湖内沿近岸到近岸的梯度。这项研究要检验的主要假设是，微生物循环过程和浮游动物循环磷的相对大小可以预测地随总初级生产力和磷缺乏指数的变化而变化，从而使不同湖泊中不同比例的循环磷被藻类和细菌结合。这项研究工作将把明确的磷通量动力学模型与旨在量化伊利湖、休伦湖和密歇根湖细菌、原生动物和后生动物循环率的相对贡献的实验相结合。一种适用于淡水调查的新的分析方法(镁诱导共沉淀法)使用稀释法研究磷的动态和再生速率变得容易。

9508087 Lehman Differences in availabilities and rates of supply of phosphorus to the ecosystems of the Great Lakes of North America are known to be major factors controlling rates of productivity, biomass development, and species composition. Nonetheless, epilimnetic concentrations of phosphate are uniformly low in all the Great Lakes during summer, and radiotracer studies demonstrate that turnover times of the ambient pools are minutes to tens of minutes, as the result of biological processes. In situ concentrations during the productive summer months have generally proven intractable to accurate measurement, but it appears that, in common with oceanic observations of ammonium dynamics, bacteria dominate fluxes at ambient levels, whereas phytoplankton dominate when concentrations are modestly increased. There are differences between turnover dynamics and equilibrium partitioning of tracer P in Great Lakes of differing trophic condition, and along inshore-to-offshore gradients within individual Great Lakes. The main hypothesis to be tested in this research is that the relative magnitudes of microbial recycling processes, and of P recycling by zooplankton, change predictably with overall primary production, and with an index of P deficiency, such that different proportions of recycled P are incorporated by algae versus bacteria in different lakes. This research effort will combine explicit kinetic models for P fluxes with experiments designed to quantify the relative contributions of bacterial, protozoan, and metazoan recycling rates in Lakes Erie, Huron and Michigan. A new analytical method adapted from sea water for fresh water investigations (magnesium inducted coprecipitation of P) now makes tractable the investigation of P dynamics and regeneration rates by is tope dilution methods.